Unnerving, Unweaving, Understanding
My first encounter with a horseshoe crab
Garrett Kincaid | Jul 20, 2025
The general rule in nature is that the live things are soft within and rigid without. – Annie Dillard1
Yesterday, for the first time this summer, I woke up in time for sunrise, the occasion being the beginning of a vacation on Long Beach Island. From a rooftop deck my girlfriend Taylor and I could see both the ocean and the bay and, beyond that, mainland New Jersey. A lemon-orange glow was spritzing and zesting itself over the thin barrier island, from north of east; and directly opposing the light, from south of west, approached a broad and pregnant storm-cloud. Water had broken. Delivery was imminent.
Taylor went back to sleep, and I walked towards the beach. As soon as I stepped outside, I stopped on the sidewalk to gawk. Bridging the opposing could-continents was a tall and bold rainbow. On the underside, violet seemed to be reaching back around to red and, on the top side, red back around to violet. I knew the rainbow to be infinite and revolving, that the segment I saw was only an arc of an otherwise invisible circle, but I had never thought about the horizontal revolutions, how the ribbon frays and bleeds at both sides and is sort of woven back into itself, made cylindrical.
It was 6:00 a.m. on the Monday before The Fourth of July. When I reached the beach, there was no one else out there other than two men in CATs reinforcing the dunes.
A little further north, near the next lifeguard stand, there were two dark, stomach-sized masses on the sand. One looked like it might be a kid's plastic shovel left over from the weekend. As I walked closer, I saw that the masses were organic and no doubt heartier than cheap plastic. Neither moved as I walked between them. The one to my left, further up the beach, was right-side up and had its backside buried. The other one was upside-down and just above the line of the tide. After seeing the shell of the one and the exposed underside of the other, I could identify both as horseshoe crabs, though I had never seen one before. Our common name for these animals is apt; indeed, their shells are shaped like a horse's hoof, but both of these shells would have been too big for the shoe of any stallion I have ever seen.
I approached the capsized crab slowly. Seeing it there in the sand was like spotting a tick on my inner-thigh: unnerving. There was nothing inviting about either its appearance or its posture: gray-green barnacles attached to the side of its shell; parasitic legs folded together in two columns of neat rows; and an erect and alert, spiky stinger that was as long as the rest of its body, like a ray's. The stinger was pointing up at me.
Can it fire that thing like a missile? I wondered. Is it luring me in by exposing its soft side? Is that one of the battle-tactics it has honed through eons of evolution? Or is this just a June bug on its back?
It was hard to imagine something so menacing as being helpless or vulnerable, but I tried to take an unbiased and fearless look at the thing. I thought, Maybe its stinger isn't an armament at the ready but like a dog's tail, trying to communicate something.
Still, I hesitated to help the thing. Growing up in Kansas, I killed every wolf spider I ever saw, at least after the age of four. At that age, during a trip to the lake, my parents and I discovered an itchy lump on one of my jewels during bath time. Mom said we should give it a day and see if it was still bothering me. But Dad insisted: "You don't mess around with these kinds of things"—because, of course, my jewels were also the family's. The next person to examine them was the doctor at the emergency room who diagnosed me with Summer Penile Syndrome, which is a pseudo-condition that requires no treatment and commonly afflicts young boys whose legs aren't much longer than the grass they've been running around in. I had always remembered that ordeal having been caused by a spider-bite, but it was more likely a chigger. Either way, the experience led me to regard all many-legged things as existential threats to my bloodline, which informed by first impression of the horseshoe crab.
Should I let it die? I wondered. What if it sits in the shallows and, later today, impales a kid at play? Would I be betraying my species by helping a thing so threatening? Thankfully my pre-frontal cortex had grown enough since I was four-years-old that I could pause and recalibrate. I decided that my fear was irrational and that my snap-judgments had been unfair.
I flicked the lip of the crab's shell to let it know I was there, and its whole form teetered atop the water-hardened sand. It responded by articulating its many little legs; every spindly extremity wiggled, bending somewhat at every joint before they each returned to rest. Its legs moved like the typebars on my Corona Standard when I can't quite find the next word; I'll flit my fingers across the mechanical keys of the typewriter and depress them halfway—not advancing the carriage or making any marks on the page—such that the typebars sort of bob up and plunk down. I recognized the crab's state of confusion and uncertainty as one of the utmost vulnerability. Like me when I am stuck in the middle of a sentence, the thing didn't know what was coming and couldn't get where it was going.
I stood between the crab and the water, and it was reaching back at me with its stinger. I looked out to the breaking waves, trying to read them. I wanted to time my move so that the crab would know which way the water was. A couple small waves were about to double-up on each other. I pulled up on the port-side of the crab's shell and flipped him over. Seawater washed over my toes and came to meet the crab. It dropped its shell down and sealed itself in, at home again.
That's when I noticed the three discrete parts of its body. The thick, broad shell—yes—did resemble a horseshoe but also reminded me of the head of a hammerhead shark, because of the shell's broad face and how closely the crab's chitin matched the tone and toughness of shark-skin. Then there was the abdomen (also armored), which had fleshy hinging-and-bending mechanisms on either side that connected it to its head and tail; the abdomen was rimmed with spikes in the same orientation and style as those on the beard of a bearded dragon—all to protect its lobster-like gills. The final segment was its rigid, needle-shaped tail, which accounted for the majority of its menacing-ness. The two shells and the tail are joint-less, like our skull, ribcage, and femur, respectively; all of the crab's movement happens in the links between the three segments. The bigger, stronger legs lift up the shell and move it only inches at a time, at least on land, and the abdomen bends and hinges so that the tail can flex up or down. The tail seems to have less horizontal mobility, though, which means that its socket-joint is more like the human hip than the shoulder.
He moved a few inches every couple minutes by heaving up his shell, crawling a single stride forward with each of its legs, and then setting it down again. Sometimes he would scoot forward without lifting the brim of his hat, which maneuver would build of a bank of sand on either side of his center, like a snowplow clearing a single-lane road. And when the tide would come up to him, he would quickly drop down his helmet-home, as if he didn't quite like the water or at least didn't like being splashed in the face.
Each time he lifted up his shell, I squatted down and peered underneath it. I saw each of his legs bending, pressing, stretching—his whole body inching. I got square with him and looked at the rim of the shell. It was shaped like a human's upper lip if the central divot were inverted (such that one's two front teeth would always be exposed). I assumed that the upturned lip was a little window for his eyes and mouth. I squatted down and titled my head so that my eyes were as close to the sand as possible (without giving up my footing and assuming the vulnerable prey-position of lying prone), and I watched him crawl towards the sea-foam, lifting his many pointy little legs from the wet sand. They were a deep brown, and the front legs' spherical joints were glistening. It was like looking into a massive oyster and seeing several ripe but unwanted pearls. I couldn't spot the crab's eyes, only his legs and what looked like a mouth in the middle of it all.
Peering underneath the crab's shell, I was aware that this was one of the most intimate experiences I've had with a wild thing. Has God, even, ever seen the underside of a horseshoe crab as it walks in the sand? Or maybe, rather than imagining God as looking down, I ought to imagine Him as having an eye within every grain of sand: many eyes, a compound eye seeing all. It no longer felt like I had discovered a tick on my thigh or a wolf spider under my bed. Instead, this experience with the horseshoe crab reminded me of the feeling I had the first time I held a roly-poly in my palm.
A name sprang to mind for the crab, and I said it aloud: "Hello, Armando." I had no way to know which gender it was, but maybe I guessed male because I was identifying with him. For me, Armando evokes the image of a cowboy, and this cowboy is wearing a Medieval knight's helmet and a breastplate. He's riding a horse with an American saddle, but rather than hip-holstered pistols or a saddle-slung rifle, Armando is holding a jousting lance under his arm and pointing it backwards.
After recovering from my initial reaction to Armando's appearance, I couldn't imagine him being parasitic or oppressive. The horseshoe crab has a quiet and pensive power, which is the most noble kind. It's the kind of power one acquires by becoming skillful, by achieving mastery. I imagined that Armando only ever uses his intimidating tail as a way to say, "Don't tread on me."
The storm-clouds had erased the rainbow and blocked the sun. It started to pour, and the sky turned darker than it'd been before dawn. Armando seemed to be in good condition, so I left the beach to go read about horseshoe crabs.
John Keats, in his poem "Lamia," warns that analysis dispels Nature's mystery, that rationalism kills wonder: "Do not all charms fly / At the mere touch of cold philosophy?"2 He describes the anti-romantic business of analysis as "unweaving the rainbow." Keats means that to reduce something so awe-some and wonder-full as a rainbow to the physics of light-refraction, for instance, is to "clip an Angel's wings," to "empty the haunted air," to "conquer all mysteries by rule and line."3 Keats places analysis and science at odds with wonder and romance, but this has not been my experience. His theory does not hold in the case of my first encounter with a horseshoe crab. By researching this animal's anatomy and physiology and history, something that was foreign and, at first, frightening to me became more awesome and wonderful, even if it did dispel some of the initial mystery.
I couldn't believe how much I had failed to see in my twenty-odd minutes of naked-eye observation. The more I learned about Armando's species, the more I related to him—for one, because I too know what it's like to be misunderstood and how it feels for someone's first impression of me to betray my essence.
Horseshoe crabs are not violent; their tails (more accurately, telsons) are not stingers but more like oars or rudders. In the northeastern U.S. from mid-May to mid-June, horseshoe crabs come ashore to mate. (It seems that the two crabs I saw had procrastinated; it was June 30th.) The main risk of this adventure is that—either on the way out or on the way back in—the crab could tumble in the surf, get turned around and stuck in the sand with its legs and mouth exposed to the sun. When capsized, the horseshoe crab uses its telson to right itself, and the telsons can easily be fractured or altogether break off from the body. Their tails are neither stingers nor missiles; horseshoe crabs have no ballistic capabilities.
As we've discussed, horseshoe is apt, but I learned that crab is a misnomer. Horseshoe crabs are more closely related to arachnids (wolf spiders, chiggers, and ticks, et al.) than they are to crustaceans. These "living fossils," as they are called—these ancient invertebrates—are better adapted to life than many fleshy or furry spine-having mammals. Horseshoe crabs seem to have cracked the code. They have existed for 450 million years, and they have not evolved much in past 200 million years, because there has been no need. They have survived ice ages and glaciation, extreme heat and volcanism, and extinction events like the asteroid impact that killed the dinosaurs (and 75% of all species living on Earth at that time). There I had been imagining a horseshoe crab as harmful, and then as being helpless, but Armando was neither.
All her life, Taylor has been fascinated by plants and animals, and by marine life especially. She has no shortage of fish-facts. And when I was sharing with her what I'd learned about the horseshoe crab, she was finishing my sentences. Taylor already knew that horseshoe crabs are harmless and scoffed at how squeamish I had reported being about seeing one on the beach.
"Do you know what color their blood is?" she challenged.
"Bright-blue," I said, and then retorted: "Did you know that we use horseshoe crab blood to develop medications and vaccines?"
"Yeah, that's how I know that their blood is blue," she said.
I explained to Taylor that I had also mistaken Armando's shell to be like that of a conch or snail. I learned that the horseshoe crab's shell is less like a house or a helmet than it is like the human skull; it is wound and bound together by essential components of the nervous system. Its two main eyes are set into each side of the shell, and between those two eyes, within the shell, are its brain and heart and mouth.
Horseshoe crabs have ten eyes in total, depending on how you count them: two compound eyes, each with a thousand individual light-sensitive facets (ommatidia), and eight simple eyes. In many ways, horseshoe crabs can see more than you and me. Two of their eyes are dedicated to sensing ultraviolet light, and their compound eyes are so sensitive in low light that they can navigate with ease by moonlight alone. I had been peering underneath Armando's shell to catch his eyes, expecting them to be like a hermit crab's, but he could see me the whole time. It was I who was the sense-less one trying to play peek-a-boo with a ten-year-old.
I now have no doubt that Armando also saw that rainbow, but let's unweave things a little further. We know that horseshoe crabs can see green and ultraviolet light, and, knowing that, I can imagine how that rainbow may have appeared to Armando. What I saw as a broad, prismatic ribbon arcing down from dark clouds the horseshoe crab may have seen as a thin, green string of light bathed in the diffuse ultraviolet radiance of the early morning. Maybe what Armando saw was something more like what I saw once just after dusk in Iceland: aurora borealis—a faint and verdant wisp of magnetized solar wind—against the deep-purple backdrop of the rising night.
Of course, I can never know exactly how Armando experienced that rainbow. For no matter how precise our measurements or how refined our methods become, something will always remain inaccessible to us—or at least immeasurable—, because we are limited by our perspective. We cannot see through the horseshoe crab's compound eyes. Our eyes are simple, and "our life is a faint tracing on the surface of mystery,"4 which is why there is no risk in analysis and only depth and detail to gain from it; we have no hope of exhausting Nature's mystery.
An example: From my perspective, the sun is small enough that I can smother it with one hand. Even though I know it is large, I have struggled to comprehend how large, because of how small it appears to be. Seeing it in the sky, one might wonder: How could the sun be so warm and so bright if it is so small?, which is the wrong question. I only began to understand the scale of our sun after learning these two figures: that (1) light from the sun takes more than eight minutes to reach Earth and that (2) the speed of light is ~300,000,000 meters per second. After doing this rote analysis, this cold philosophy, one might then wonder: If the sun is an entire eight light-minutes from Earth, why does it appear to be the same size as the moon in the sky? And that is the right question. It's a question that leads one further into wonderment, via one final step in the analysis: light takes 500 seconds to travel to us from the sun and only 1.3 seconds to travel from the moon, so the sun must be about 400 times as far from Earth as the moon is, and since they appear to be the same size in the sky, the sun must be 400 times the size of the moon!
Now, it may seem like we have answered the question How big is the sun? and thereby dispelled the mystery, but we have done no such thing. We have only confirmed that the size of the sun is incomprehensible. And unweaving one mystery, we have unraveled many more: How far away is the next-nearest star? The nearest galaxy? How old is the light that we receive from that star? From that galaxy? Could we ever look far enough that we see some of the earliest light in the universe? What appear to be seven threads in the rainbow's ribbon are each ribbons of their own; ROYGBIV is not a spectrum of colors but a spectrum of spectrums. Every thing that weaves is also woven. Thus, the final analysis of Nature will not dispel mystery but rather corroborate it by failing to account for Her total scale and intricacy. The horseshoe crab has two thousand and eight eyes—how unfathomable is that?!
Later, Taylor told me, "You know, I saw a horseshoe crab on the beach last year. It was in the sand by one of those rock barriers. I picked it up and carried it out past where the waves were breaking."
"You just picked it up?" I asked. "How did you know how to hold it? Did you grab it from the top?"
"No, from the bottom. I could see its legs and mouth, and its tail was bending toward me," she said.
"And why'd you wade into the water with it?" I asked.
"That's what you're supposed to do. They have a hard time crawling back into the water, especially in bad weather, 'cause they get turned around in the surf. Oh! And the lifeguard yelled at me. Can you believe it? I clearly wasn't going to swim there."
"You never mentioned that," I said. "I would have remembered."
"Well, it wasn't a big deal." ❛❜
Springboard
A carefully crafted question to help you dive inwards:
Footnotes
- Pilgrim at Tinker Creek (Harper Perennial Modern Classics, 2013), 92. (I have been reading this book and writing this essay concurrently, and Annie Dillard has strongly influenced the structure and style of what follows.) ↑
- John Keats, "Lamia," in Gutenberg.org, accessed on July 11, 2025, https://www.gutenberg.org/files/2490/2490-h/2490-h.htm. (I was introduced to this poem and this quote by Robert Macfarlane, which he shared during his interview on the How I Write podcast.) ↑
- Ibid. ↑
- Dillard, Tinker Creek, 11. ↑
References
- "Horseshoe crab blood: the miracle vaccine ingredient that's saved millions of lives" – Natural History Museum, London
- "Facts About Horseshoe Crabs and FAQ" – Florida Fish and Wildlife Conservation Commission
- "What We Learned About Vision - from Horseshoe Crabs" – 20/20
- This conversation with ChatGPT, which includes some research and fact-checking